[1]. Purpose :In this study, we investigated whether the polymorphism of estrogen receptor (ER) and ACE gene had any effect on the clinical or histological prognosis of IgA nephropathy.[2]. Material and Method :74 children with IgA nephropathy, who were treated with the protocol including prednisolone for 2 years, and serial renal biopsy could be performed after treatment, were included in this study. DNA was extracted from peripheral mononuclear cells, genes of ER and ACE were amplified by PCR and polymorphism of them were examined with RFLP. The relation of clinical parameters of children with IgA nephropathy and polymorphisms of these genes were analyzed.[3]. Results :(1) In the polymorphism of ER gene, 9 were PP (18.3%), 35 were Pp (71.5%) and 5 were pp (10.2%). 25 patients cold not be studied or their genes could not be amplified.(2) In the polymorphism of ACE gene, 14 were II (25.9%), 28 were ID (51.9%) and 12 were DD (22.2%). 20 patients cold not be studied or their genes could not be amplified.(3) Chronicity index was significantly reduced by treatment in the children with PP, but not changed in the children with Pp and pp.(4) Before treatment, activity index was significantly high in the children with ID and DD, compared with the children with II. Although statistically not significant, chronicity index after treatment was higher in the children with ID and DD. There was no patient with II, whose urinalysis became worse after treatment. On the other hand, it worsened in some patients with ID and DD.